1. Field of the Invention
This invention relates to electrostatic speakers. More particularly, it relates to a modular, non-hybrid electrostatic speaker system wherein the electronic circuitry, including the power transformer, is removed from the cabinetry of the speaker housing and enclosed within a central unit wherein a single printed circuit board is employed for each electrostatic speaker employed within the system.
2. Description of Prior Art
Electrostatic loudspeakers, also known as capacitor loudspeakers, are well known in the prior art. Electrostatic speakers work on a physical principle quite different than that of cone and dome style speaker. Electrostatic speakers employ an ultra-thin layer of electrically charged conductive film (the diaphragm) sandwiched between two metal grids or stators along with a set of spacers. The spacers provide the diaphragm with a fixed distance in which to move backwards and forwards between the stators. A DC power supply coupled to each speaker supplies a substantially constant charge to the stators such that when an amplifier sends an audio signal to the speaker, the signal changes into a high voltage signal which are applied to the stators being equal in strength but opposite in polarity. As signals are applied to the stators, the resulting electrostatic field works conjunctively with and against the diaphragm to move it back and forth thereby moving air particles which the human ear detects as the audio signal emanating from the audio source.
Known prior art electrostatic speakers are known as xe2x80x9chybridxe2x80x9d speakers since they usually employ a cone or dome style speaker driver along with the electrostatic driving element. This has been done since a typical electrostatic speaker is unable to produce low-end audio frequencies, such as, for example, those frequencies below 150 Hz. As shown in U.S. Pat. No. 4,122,302, a typical electrostatic speaker system is disclosed wherein a dynamic speaker (cone driver) is employed in combination with the electrostatic speaker element. This xe2x80x9chybridxe2x80x9d style represents a deficiency in the prior art since some form of crossover circuitry must be employed within the electrostatic cabinetry to direct the appropriate audio frequencies to either the dynamic driver or the electrostatic element. This takes away from one of the main advantages of an electrostatic speaker in that it can not be made to be generally planar in shape. Some form of box-like cabinetry must be employed with the electrostatic element to house the crossover circuitry and the dynamic driver. In most cases, this eliminates, or at least limits, the ability to mount an electrostatic speaker to a wall. What is needed is a completely planar electrostatic speaker housing that lacks any box-like housing so that it could be mounted to a wall surface, much like a flat plasma TV screen can be mounted to a wall as compared to a traditional CRT TV set. It is understood that most electrostatic speakers are referred to as being xe2x80x9cgenerallyxe2x80x9d planar, however some do employ a convexed-shaped, faceted, or curved stator assembly, for example, like those produced by the company MartinLogan(trademark). What is meant by xe2x80x9cgenerallyxe2x80x9d planar, is that the overall housing of the speaker is generally flat as compared to the square or rectangular shaped housings which encloses cone or dome style drivers. These housing require a substantial amount of depth to enclose the magnetic voice coil and cone-shaped driver.
As stated before electrostatic speakers employ a power supply for each electrostatic speaker within a system. This is done to xe2x80x9cchargexe2x80x9d the stators and create the electrostatic field which acts to move the diaphragm back and forth. The need for each electrostatic speaker to have its own power supply is an inherent disadvantage in the prior art which needs to be improved upon. Typically, prior art electrostatic speakers are provided with an AC plug coupled to a 12 volt DC converter. Accordingly, each electrostatic speaker must be setup in close proximity to an AC socket or attached to a multi-plug AC power strip which in turn is plugged into an AC socket. In either case, locating the electrostatic speaker can become more dependent on the location of its needed power source instead of its optimal acoustical positioning. Due to the inherent unidirectional sound dispersion characteristics of electrostatic speakers, location is often critical to the sound reproduction. A so called xe2x80x9csweet spotxe2x80x9d is often created in an electrostatic speaker system which is not considered as critical of a factor as that of the more inherent omnidirectional dispersion characteristics of cone or dome style driving speakers. Therefore, the dependency upon the location of the power source has been a major deficiency in prior art electrostatic speakers and systems; one which needs improvement.
It is clear from the prior art, that major inherent deficiencies and disadvantages exist for known electrostatic speakers that warrant improvement thereupon. First, there is clearly a need to provide for a non-hybrid electrostatic speaker. This would eliminate the need for additional housings to be employed with the generally planar electrostatic speaker since no cone drivers would be employed. There is a further need to xe2x80x9cde-couplexe2x80x9d the electronic circuitry from the electrostatic speaker thereby permitting for ideal acoustical positioning. Centrally locating all electronics for a given electrostatic speaker system would also represent an improvement in the prior art. Still further, providing a single power source for all of the speakers of an electrostatic speaker system would greatly improve the ability to locate the speakers for both acoustical (xe2x80x9csweet spotxe2x80x9d) and aesthetic purposes. And since surround sound is a greatly desired feature of most audio systems of today, an electrostatic speaker system which permits for additional speakers to be added with great ease, such as in a modular fashion, would also be a great advancement in the prior art of electrostatic speakers and systems. Further, the ability to add a non-hybrid center channel electrostatic speaker would be an advancement in the prior art since none are known to exist therein.
I have invented a modularly expandable electrostatic speaker system which greatly improves upon known prior art electrostatic speakers and systems. Each electrostatic speaker within my novel system is a non-hybrid, purely electrostatic speaker. Hence, there are no magnetically driven cone or dome style drivers utilized with my electrostatic speakers. Each speaker employs a diaphragm made of an ultra-thin layer of electrically charged conductive film positioned between the stators which are separated by a set of spacers. The diaphragm, having a mass less than the air it moves, pulsates back and forth in response to the oppositely charged stators.
A constant charge is applied to the stators of each speaker from a single power supply within a central unit. Also within the central unit, coupled to an A/V receiver or amplifier (which in turn is coupled to an audio source), are a series of slots which receive a plurality of printed circuit boards (PCB). There is one PCB for each electrostatic speaker employed within the system. The single power supply employed within the central unit supplies power to all of the electrostatic speakers of the system. There is no need in my system to supply power to each speaker with a separate power source (i.e., AC adapter plugged into a wall socket for each speaker) as in known prior art electrostatic speakers. Power is supplied to each speaker in my system through a single cable coupled between the central unit and each speaker which also happens to carry the audio signal. Of course the power source cable is well shielded from the audio signal cable to eliminate any potential interference there between.
Since my system is modularly expandable, the system can employ two speakers to five speakers (i.e., front left and right, center, rear left and right) in the preferred embodiment. In alternate embodiments, my system could actually employ even more speakers (i.e., a six speaker system wherein a center rear is employed). It is of course understood that my system can also employ a subwoofer which is coupled directly to the A/V receiver (controller) or amplifier. My novel electrostatic speakers, along with the central unit, are therefore capable of decoding and thereby producing audio sources encoded with any of the known surround sound technology, such as, for example, Dolby(copyright), DTS(copyright) and THX 5.1(copyright).